Introduction
DNA fingerprinting also known as DNA testing, profiling or testing is used to identify individuals based on their DNA profiles. Although sequences of DNA are commonly found in human beings, profiling of DNA uses variable repeat sequences otherwise known as (VNTR). DNA fingerprinting is applied in some areas which include; crime investigation, personal identification, disease fighting as well as fighting fraud. Other applications are the diagnosis of disorders that are inherited as well as developing their cure. DNA fingerprinting process follows a procedure starting with DNA isolation, cutting, sorting and sizing; DNA is then transferred to a nylon sheet where probing is done.
DNA fingerprinting
According to (Salvas, 1994), DNA fingerprint is the fingerprint that cannot be changed by surgery or treatment and it is similar for each and every organ, tissue and cell in one’s body. DNA fingerprint has been used widely in distinguishing as well as identification of living organisms and different living organisms give different sequences of DNA.DNA fingerprints have applications in different research areas of human health and in the system of justice which include diagnosis of disorders inherited in babies to assist in treatment. It’s also used in solving cases where children’s parents need to be identified or in confirmation of ones nationality. VNTRs are inherited from ones parents and resultant patterns of VNTRs help establish maternity or even paternity.
In crime investigation, comparison is done between VNTR patterns of fingerprint’s DNA from evidence collected at the crime scene with that of a suspect of crime to determine innocence or guilt. Another application that has not received popularity is where fingerprints in form of bar codes of genetics are used in identification of individuals because the technology used is impractical as well as expensive. In fighting of diseases, DNA fingerprinting has been used in identification of strains that are resistant to antibiotics where doctors select an alternative antibiotic. DNA fingerprinting is also used by pharmaceutical manufacturers to label medicines which enable easy detection of counterfeits while producers of wine use it in ensuring that the right grapes are used in wine making to guarantee authenticity. (Salvas, 1994)
(Bennett, 1995) argues that, DNA fingerprinting is not 100% perfect in giving results because of problems with probability. VNTR pattern only gives the probability that the given person is the owner of that pattern and this is supposed to be very high mostly in cases of crime. Probability of two samples of DNA can be increased by using VNTR combinations or VNTRs that are rare in creation of VNTR pattern.
A practical report on DNA fingerprinting
According to (Joly, 1997), the exercise of DNA fingerprinting takes place in a laboratory where a procedure is followed requiring DNA isolation as the first step. Here, DNA is recovered from body tissues or cellular material either chemically where a detergent is used to separate DNA from extra material or mechanically where DNA is squeezed out by applying so much pressure. The next step is cutting of DNA into different sizes using restriction enzymes also known as sizing, followed by sorting of the pieces of DNA by size.
This is done through gel electrophoresis process where DNA is placed on gel followed by application of electrical charge resulting to positive charge coming beneath the negative charge. Since DNA has negative charge, DNA pieces are attracted to the bottom with small pieces moving faster than large pieces hence the separation of DNA pieces by size.
Denaturing follows where single strands of DNA are made by treating it chemically or heating in gel which is then applied on a paper and baked to attach it permanently on the sheet. Probing is done by adding colored or radioactive probes to the paper producing a DNA fingerprint with each probe sticking in one particular part of the sheet or even two places. Each DNA strand has pieces with genetic information informing development of organisms known as exons as well as pieces that don’t supply any genetic information known as introns.
Introns are not useless as they seem because they have base pairs’ sequences that are repeated otherwise known as Variable Number of Repeat Tandoms (VNTRs). Everybody has VNTRs inherited from the father, mother or both. Determination of whether one has VNTR of a particular kind involves the above process resulting to a pattern known as DNA fingerprint. (Wilson, 2000)
References
Salvas Y. (1994): PCR and DNA Fingerprinting: Am Soc Enol Viticulture pp. 35-39.
Joly S. (1997): Southern blot hybridization with the moderately repetitive DNA probe: Am Soc Microbiol pp. 87-91.
Bennett J. (1995): Potential use in DNA fingerprinting: Elsevier pp. 47-53.
Wilson J. (2000): Implications from random amplified polymorphic DNA: Blackwell Synergy pp. 68-73.
Burke T. (1998): Multilocus and single locus DNA fingerprinting: Oxford University pp. 19-23.
Kapur V. (2002): DNA Fingerprinting of Pastesurella multocida: Am Soc Microbiol pp. 56-59.